Sellwood Bridge span could be become detour bridge during construction

UPDATE • County officials hope to accelerate work and shave 'millions' from cost of the replacement project

Multnomah County officials hope that by building a temporary bridge next to the crumbling Sellwood Bridge they can accelerate the project and save possibly 'millions' in construction costs.

Mike Pullen, county public information officer, told commissioners Tuesday morning that construction of a 'shoo-fly' temporary bridge might allow the contractor to begin work on the project this fall, instead of waiting until the summer 2012.

Pullen said the commissioners would get 'hard numbers' in about a month on the amount of money it project could save. But it could be substantial, he told commissioners during the briefing.

'We're talking about millions being saved,' Pullen said.

Plans to pick up and move the main span of the existing Sellwood Bridge about 40 feet north to become a detour bridge during construction surfaced this week. The county's bridge construction team will meet with Portland planners in mid-April to talk about the project and work out permit agreements so the temporary bridge could be used, Pullen said.

By shaving time off the construction schedule, and pushing it up, Pullen said the county would save money on the estimated $290 million work.

'We want to accelerate construction of this project, and we think we can get there,' Pullen told commissioners.

Moving some residents

The proposal is a new idea suggested by Slayden Construction Co., the firm selected as the prime contractor for the project. Slayden did the same thing with the replacement Elkton Bridge project outside of Eugene, Pullen said.

The span would be relocated about 40 feet north, turning it into a detour bridge that could be in place for up to four years. Although moving the span would close the bridge for a week, it could shave a year or more off the construction schedule, saving more money than the move would require, Pullen said.

Before the span is moved, new temporary piers would be built north of the existing bridge in the Willamette River and on both the west and east banks. Temporary supports would also be built from the side of the existing bridge.

After the new bridge is completed, the old span and temporary supports would be removed. The process is called 'shoo-fly' in the construction industry.

The county would not be required to acquire any more of the condominiums at the east end of the bridge if the span is moved. Some residents would need to move out for a month or more while a new approach ramp is built near their homes, however, Pullen said.

Changes reduce some costs

Pullen said that in addition to the time and money savings, using the existing deck for a detour bridge would improve the safety for both workers and those who use the bridge. The original plan called for rebuilding one lane of the two-lane bridge at a time, requiring bridge traffic to alternate on the open bridge.

Contracts with Slayden and lead design firm T.Y. Lin International are not expected to be signed for a few more weeks.

The commission and regulatory agencies would have to formally approve moving the deck later this year, however. Under the original construction schedule, work was not set to start until the summer 2012. If the commission approves moving the deck, work could begin by November 2011, Pullen said.

Design changes have cut the cost of the project from $330 million to $290 million. Portland, Multnomah County and the state have all committed to helping fund the project.

Clackamas County funds in question

Clackamas County's share is up in the air after residents there referred a $5-a-year motor vehicle fee to help finance the project to the May 17 special election ballot.

If voters approve the fee, the project will still be about $20 million short. The federal government has been asked to fill that gap.

If voters reject the fee, the shortfall will grow to around $40 million. Clackamas County commissioners could use funds from other sources to fulfill its commitment, however.

The Sellwood Bridge bridge needs to be replaced because of landslides at the west end that have undermined and cracked its foundations. The bridge is so weakened that TriMet buses and heavy trucks are prohibited from crossing it.

Despite that, the bridge is a major east-west commuting route. It is the only crossing for a 12-mile stretch of the Willamette River between Portland and Oregon City.

It is the busiest two-lane bridge in the state, with an average daily traffic count of 30,000 vehicles.